Femtosecond laser micro-ablation is a new high-precision processing method. In this study, the ablation characteristics of a face gear material (18Cr2Ni4WA steel) were studied. The energy coupling effect of the electronic and lattice subsystems of the ablated 18Cr2Ni4WA steel was investigated. In addition, a two-temperature model was established, and the effects of pulse width and average power on electron and lattice temperature were simulated using the finite difference method. Results reveal that when thermal equilibrium between electron and lattice is reached and the electron and lattice temperatures exceed the melting point of the material, the tooth surface is ablated; furthermore, when the electron and lattice temperatures are higher than the material boiling and phase explosion temperature, the material removal is mainly achieved by phase explosion. The material ablation depth is generally taken as ~40 nm to prevent the thermal effects on surface quality. The single-pulse ablation threshold of the 18Cr2Ni4WA steel ablated by a Gaussian distributed femtosecond laser using the femtosecond laser microprocessing system was 0.29 J/cm². The effects of average power and pulse number on the ablative morphology of the material were analyzed. The ablation characteristics of the 18Cr2Ni4WA steel microprocessed by a femtosecond laser in this study provide a technical basis for improving the processing quality of face gears.